Most cities have very minimal supplies of even what you'd consider the basics of life today. Food is grown far outside a city's borders and transported in; water purification and sewage processing is situated near large fresh water sources, and the treated product is piped in; electricity generation also happens where it's most optimal to situate power plants; and medical supplies, as well as their raw components, are also transported in and not produced there.
So the stocks of the above basics are not going to last for long. Once everyone realises that, they're going to head for the shops to try and get whatever they can. Those shops aren't going to sell those vital supplies because the people there know that they'll need them before long. The end result will be rioting, looting, and general anarchy - and that's before the supplies run out.
The end result of this rioting and looting will be at least one faction, more likely many, that control various vital resources. Supermarkets with bottled water, police stations with guns, that sort of thing. Everyone else gets to survive with whatever they had, or can steal, or whatever.
They don't survive long. A human can survive for weeks without food, but only about 3 days without water. If there is a water source on this other world, one of the powerful factions will already have claimed it - but that's not worth much, because they also need to purify it, and that's a far more difficult task. An organised faction is likely to be able to accomplish this... your average family unit, not so much. And the faction is not going to be willing to allow outsiders to use "their" water.
So people are going to start dying. Lots of people. Because you no longer have clean water or sewage processing or refuse removal facilities or law enforcement or medical services or anyone that has time for no-personal-survival-related tasks, the dead are going to lie where they fall, and they are going to rot. Which will bring disease. Which will make it even more hazardous for those who remain.
Pets will become feral. Rodents and cockroaches will emerge from the sewers. These animals will also be desperate for water and food, which will remove their fear of humans. They will feast on the dead, which will further create and spread pestilence.
Unless you are already prepared for such a nightmare scenario, there is very little you, as an average Joe, are going to be able to do to survive it. It doesn't matter how fit you are, or what superhuman powers you have - if you can't get the essentials of human life, you die.
So, the #1 predictor of survival in this scenario, is, perversely, how quickly you get out of the city. The sooner you leave, the sooner you will (hopefully) find a (relatively) clean water source that (probably) won't kill you. If you're lucky, you find native plants that you can eat (you will lose a few people with that trial and error). If you're really lucky you have some Earth crop seeds to plant, and you find somewhere to plant them, and you actually know how to make them grow, and they don't get eaten or destroyed by rain or native animals, and they produce enough to feed everyone in your group.
All of this is ignoring the native flora and fauna on this world. This includes bacteria and viruses (or whatever the native equivalent is), which as H. G. Wells demonstrated, could conceivably be the most deadliest thing of all.
In short, what you have is a situation that's orders of magnitude worse than any zombie apocalypse. 20% of the population surviving would be a miracle; I think 2% would still be a stretch.